近断层方向性效应地震作用下曲线梁桥试验

Experimental study on curved girder bridge under near-fault ground motion with directivity effect

摘要:

为研究近断层方向性效应地震对曲线梁桥的影响,以一座曲线梁桥为研究对象,设计制作了缩尺比例为1∶10的全桥物理模型,选取破裂前方区域（forward region,FR）、破裂区域（middle region,MR）和破裂后方区域（backward region,BR）地震动,进行地震动模拟振动台试验。试验结果表明:FR地震动和MR地震动作用下曲线桥地震响应较BR地震动显著；单向激励时,MR地震动作用下结构响应明显,双向地震激励时,结构响应则和曲线桥与破裂方向相对位置有关；曲线桥垂直于破裂方向单向激励时,主梁绕固定墩产生水平转动,双向地震激励时,FR地震动和MR地震动作用下主梁的转动效应较BR地震动显著；相对于BR地震动作用,FR地震动和MR地震动对桥墩切向位移的放大作用大于径向位移的放大作用；曲线桥垂直于破裂方向时,主梁更容易产生转动,使得支座位移响应和梁端位移响应在低墩处显著,在抗震设计时,应合理分析避免支座脱落或落梁.

Abstract:

To study the influence of near-fault ground motion with directivity effect on curved girder bridges, a whole physical model of curved girder bridge with the scale ratio of 1∶10 was designed and manufactured, the ground motions in forward region (FR), middle region (MR), and backward region (BR) were selected, and seismic simulation shaking table test was carried out. Experimental results show that the seismic response of the curved bridge under the action of FR ground motion and MR ground motion was obviously higher than that of BR ground motion. In the case of unidirectional input, the structural response was greater under MR ground motion, while in bidirectional input, the structural response was related to the relative position of the curved bridge and the rupture direction. When the curved bridge was perpendicular to the rupture direction and the unidirectional input, the main girder rotated along the fixed pier. The rotational effect of the main girder under FR ground motion and MR ground motion was more obvious than that under BR ground motion in bidirectional input. The amplification effect of pier tangential displacement under FR ground motion and MR ground motion was greater than that of pier radial displacement. When the curved bridge was perpendicular to the rupture direction, the main girder was easier to rotate, making the displacement responses of the bearing and the beam end larger at the low pier. Therefore, in seismic design, rational analysis should be performed to avoid bearing shedding or girder falling.